Laminated-Veneer-Lumber (LVL) (sometimes called Parallel Laminated-Veneer) is a lumber-like product belonging to the family of man-made wood composites. It is produced by laminating rotary-peeled veneer sheets into billets of desired thickness, width and, generally, of continuous length. The billets are further processed into required dimensional sizes. The product has a strong resemblance to plywood, but there are noticeable differences. LVL is produced in thicker panels and of continuous length. In LVL, all veneer sheets are assembled with the grain orientation parallel to the longitudinal axis of the panel to maximize the finished product's strength in the longitudinal direction. Such an arrangement makes the LVL suitable as a direct substitute for structural lumber.
An LVL product has some important advantages over sawn natural lumber. It can be produced in sizes difficult or impossible to obtain in solid wood. It retains the wood's machinability qualities but gains improved uniformity of mechanical properties. Another important attribute of LVL is that an increased yield from a long can be obtained. Peeling utilizes the whole long thereby leaving only the core for further processing. A recovery increase of 40% to 50%, when compared to sawn lumber, has been reported and is due mainly to elimination of losses due to sawinq. Dependable design strength is achieved by randomizing the concentrated defects inherent in wood throughout the volume of the product and thereby minimizing their effect on the strength.
Notwithstanding the foregoing important advantages, LVL production processes introduce certain variables which have a detrimental effect on the product's strength. Veneer jointing is one such variable. Existing systems for production of LVL use the same or similar veneer preparation methods as those that have been developed in the past for plywood manufacture. The veneer is rotary-peeled from the circumference of a log in thicknesses most commonly ranging from 1/10" to 1/4". Such peeler logs are usually eight feet long. The peeled ribbon of veneer is unrolled and subsequently clipped into planar sheets and dried. Since LVL products are manufactured in lengths exceeding that of a veneer sheet, the veneer sheets must be joined to form the desired lay-up length. The type of joint that is used in the lay-up therefore has a significant impact on the product's overall strength. Veneer joints that are currently in use in lay-up production are (a) butt, (b) overlap, (c) scarf, or (d) vertical finger joint. The butt and overlap joints are the simplest and most economical to produce, but they also suffer significant loss of strength of the finished product due to discontinuity and created stress concentrations. The strength loss associated with the scarf and vertical finger joints is less than with the butt and overlap joints. However, the scarf and finger joints are more expensive to produce. An additional operation is involved in each case, and this operation is necessarily accompanied by a waste of raw material.
Three United States patents disclose processes for producing jointed veneer products.
Forsyth (U.S. Pat. No. 1,222,616) discloses rotary-peeled veneer sheets which are subsequently cut and assembled to form a layered structure.
Harwell (U.S. Pat. No. 1,924,240) discloses a method of making compound lumber. The method includes edge-wise joining of strips of wood by mating curved edges.
Corbin (U.S. Pat. No. 2,382,208) discloses a method of making a structural element by cutting stock to produce sinuous cuts with subsequent reassembly of the cut sections.
None of these patents discloses cutting veneer sheets with sinusoidal edges using a log with angled ends.